Elle Fanning and Sarah Paulson head I Am Sybil cast

Elle Fanning and Sarah Paulson are to star in 'I Am Sybil'.

The pair have boarded the movie that is to be co-written and directed by Mirrah Foulkes.

The picture is to explore the true story behind the cultural-sensation case of Sybil, one of the first mainstream cases of dissociative identity disorder (formerly known as multiple personality disorder), which raised questions in the public consciousness around identity and mental health.

Sybil was a pseudonym given to art teacher Shirley Mason in a 1973 work of non-fiction by Flora Rheta Schreiber – which assessed her treatment for multiple personality disorder by psychologist Connie Wilbur.

The film will draw on Debbie Nathan's 2011 book 'Sybil Exposed: The Extraordinary Story Behind the Famous Multiple Personality Case', one of several texts that disputes Schreiber's account of the case.

Sources say that Fanning will play Mason with Paulson starring as Wilbur in the movie.

The story has previously been adapted for two TV movie adaptations. The first starred Sally Field and Joanne Woodward in 1976 and won four Emmys.

The second premiered in 2007 and featured Tammy Blanchard, Jessica Lange and JoBeth Williams.

Foulkes is directing from a script she has penned with Jen Silverman. Producers include Jennifer Todd, Ellen Goldsmith-Vein and Lindsay Williams.

Meanwhile, Elle is set to star in the Bob Dylan biopic 'A Complete Unknown' with Timothee Chalamet and Monica Barbaro.

The film is being directed by James Mangold and will star the 'Dune' actor as Dylan with Elle portraying the 'Blowin' in the Wind' singer's early 1960s love interest, the university student and artist Sylvie Russo.

'A Complete Unknown' focuses on a transformative moment for Dylan as he shook up his folk music act by going electric at the Newport Folk Festival in 1965. The move proved divisive amongst his fans and the music scene but put the music icon on the path to recording some of his greatest songs and albums.